1. Field of the Invention
The invention relates to a system for controlling a mechanism that transmits power for a travel of a vehicle. The invention particularly relates to a control system for a power transmission mechanism that includes a selectable one-way clutch.
2. Description of Related Art
The invention related to a vehicular transmission that includes a selectable one-way clutch (hereinafter described as an SOWC) is described in US 2009/0084653 A. The SOWC described in this US 2009/0084653 A includes: a first ring and a second ring that are arranged to face each other; and a strut that is arranged between these first ring and second ring. The first ring is provided with a pocket which a tip of the strut enters and is engaged with. The second ring is provided with a through opening. The strut is housed in the through opening. The strut is configured to be pushed out to the pocket side by a projecting tooth of an apply ring via a spring, the projecting tooth of the apply ring being inserted in the through opening from a back surface side of the second ring (an opposite side of a surface that faces the first ring). A combination of the strut and the pocket is provided in two types that are a first type and a second type. In the first type, the strut and the pocket are engaged when the SOWC transmits torque in a forward travel direction. In the second type, the strut and the pocket are engaged when the SOWC transmits the torque in a reverse travel direction. A blocking device is arranged between the first ring and the second ring in a manner to rotate within a specified angle range. The blocking device is a ring-shaped plate like the first ring and the second ring. This blocking device is provided with a window through which the strut passes. In addition, a return mechanism that presses the blocking device in a direction to separate the blocking device from the first ring is provided between the blocking device and the first ring. Then, the above apply ring is configured to be moved by an actuator in a rotational axis direction. Accordingly, it is configured that the second ring and the blocking device are pressed to the first ring side via the apply ring and the projecting tooth by pressing the apply ring to the first ring side by thrust of the actuator.
In a disengaged state that the above SOWC is not engaged in any of rotational directions of the forward travel direction and the reverse travel direction, the strut is pressed in the through opening of the second ring by the blocking device. In other words, the first ring is completely separated from the blocking device and the second ring. The actuator is actuated in such a disengaged state to press the second ring and the blocking device to the first ring side. As a result, the blocking device is brought into contact with an opposing surface of the first ring. The blocking device that is in contact with the first ring rotates in a rotational direction of the first ring by a friction force that is generated at this time. Then, when a position of the window of the blocking device matches a position of the through opening of the second ring (that is, the strut) in the rotational direction, the strut is pushed out from the window to the first ring side. As a result, the tip of the strut is engaged with the pocket that is formed in the first ring. In other words, the SOWC is switched to an engaged state.
Noted that the invention related to an SOWC is described in US 2013/0062151 A. The SOWC is constructed with: a strut; a notch plate that is formed with a notch, the notch being engaged with the strut; a pocket plate that is provided with a recessed section for housing the strut; a control plate that is formed with an opening through which the strut passes and that controls an engaged state between the strut and the notch.
In the SOWC described in US 2009/0084653 A above, in the case where the SOWC is switched from a disengaged state (MODE 1) to an engaged state (MODE 2), the SOWC is controlled such that a negative difference (differential rotation) is once produced between a rotational speed of the first plate and a rotational speed of the second plate. Thereafter, the SOWC is controlled such that the differential rotation speed becomes positive. The SOWC is switched from the disengaged state to the engaged state in a state that the differential rotation speed has actually become positive. More specifically, the SOWC is controlled such that the differential rotation speed, which has once become negative, is reversed to the positive side and then increased. Then, at a point of time when the differential rotation speed becomes zero, the actuator starts being actuated. With the actuation of the actuator, the blocking device is rotated by contacting with the first ring. Then, the position of the window of the blocking device matches the position of the through opening of the second ring. Accordingly, a state that the strut can be projected from the window of the blocking device is generated. In other words, a state that the strut can be engaged with the pocket is generated. Then, once the differential rotation speed is increased to specified differential rotation speed on the positive side, the strut is operated to be projected from the window of the blocking device. The tip of the strut is then engaged with the pocket of the first ring, and thus the SOWC is switched to the engaged state. Noted that, in this SOWC, a state of the positive differential rotation corresponds to a direction in which the strut and the pocket are engaged. That is, this state corresponds to a rotational state in which the torque can be transmitted between the first ring and the second ring. A state of the negative differential rotation corresponds to a direction in which the strut and the pocket are not engaged. That is, this state corresponds to a rotational state in which the torque is not transmitted between the first ring and the second ring.